This invention generally relates to golf balls and, more particularly, to a selectively weighted golf ball having at least one hollow layer and/or an improved hollow core.
Conventional golf balls have been designed to provide particular playing characteristics. These characteristics typically include initial velocity, compression, and spin of the golf ball, and can be optimized for various types of players. For example, certain players prefer a ball that has a high spin rate in order to control the flight of the ball and to stop the golf ball on the green. This type of ball, however, does not usually provide maximum distance. Other players prefer a ball that has a low spin rate and high resiliency to maximize distance.
Early solid golf balls were generally comprised of a hard core and a hard cover. Generally, if the golf ball has a soft core and a hard cover, it has a low spin rate. If the golf ball has a hard core and a hard cover, it exhibits very high resiliency for distance, but a xe2x80x9chardxe2x80x9d feel and is difficult to control on the greens. Additionally, if the golf ball has a hard core and a soft cover, it will have a high rate of spin. More recently developed solid balls are comprised of a core, at least one intermediate layer, and a cover. The intermediate layers improve the playing characteristics of solid balls and can be composed of thermoset or thermoplastic materials.
Typically, solid golf ball cores are spherical and solid. In an effort to improve the spin rate of balls, the weight distribution in the golf ball has been varied by concentrating the weight either in the spherical inner cores or in the mantle(s) near the surface of the ball. It is desired, therefore, to provide a golf ball with symmetrical, non-spherical weight distribution that provides unique spin rate characteristics.
Several patents are directed to golf balls having hollow cores, and projections emanating from the cores.
U.S. Pat. Nos. 5,820,485 and 5,836,834, issued to Hwang and Matsutani respectively, disclose solid projections on a core, the space around which is filled with outer core material, with no voids or air space.
U.S. Pat. No. 5,984,807 issued to Wai discloses a core having a plurality of projections defining an interstitial space and a layer disposed within the interstitial space. The geometric shaped core is manufactured by first providing flexible, resilient, honeycombed inserts to be used in a conventional compression mold, the inserts placed in upper and lower mold halves wherein the core material is then added and molded. But, the interstitial spaces are not hollow, they are filled with cover material.
The prior art discloses many ball patents having projections. Some of these include U.S. Pat. Nos. 5,692,973 (Dalton), 4,173,345 and, 4,229,401 (Pocklington). Many patents disclose hollow cores including U.S. Pat. No. 704,748 to Kempshall and U.S. Pat. No. 5,480,395 to Molitor.
However, these patents do not disclose a golf ball having the configuration as disclosed herein to provide the improved golf balls of the present invention.
The present invention is directed to a golf ball having a layer and/or a core geometry designed to provide improved playing characteristics such as spin rate.
The present invention is also directed to a golf ball having an improved core that comprises either solid struts, pillars or supports to produce a partially hollow core that is sectioned into hollow pockets separated by solid walls, thereby providing a durable core that has a reduced specific gravity. The struts, pillars or supports being flexible to allow the core to deform upon impact without fracturing or failing in use. It is preferable that the volume occupied by the struts, pillars or structures be less than the volume of the voided areas.
The present invention is further directed to a golf ball having at least one hollow layer, preferably placed between the innermost core and an outermost core layer. However, this layer can be placed between the outer core layer and inner cover layer, or between two cover layers. The hollow layer will reduce the specific gravity, improve feel, modify sound and/or impact response and also spin properties.
An embodiment of the invention will provide a double hollow golf ball that will combine the hollow inner core structure and encase it with a hollow outer core layer.
Another embodiment of the invention would provide a golf ball with a solid inner core and multiple hollow layers.